17,453 research outputs found
The Flow Fingerprinting Game
Linking two network flows that have the same source is essential in intrusion
detection or in tracing anonymous connections. To improve the performance of
this process, the flow can be modified (fingerprinted) to make it more
distinguishable. However, an adversary located in the middle can modify the
flow to impair the correlation by delaying the packets or introducing dummy
traffic.
We introduce a game-theoretic framework for this problem, that is used to
derive the Nash Equilibrium. As obtaining the optimal adversary delays
distribution is intractable, some approximations are done. We study the
concrete example where these delays follow a truncated Gaussian distribution.
We also compare the optimal strategies with other fingerprinting schemes. The
results are useful for understanding the limits of flow correlation based on
packet timings under an active attacker.Comment: Workshop on Information Forensics and Securit
Two and three electrons in a quantum dot: 1/|J| - expansion
We consider systems of two and three electrons in a two-dimensional parabolic
quantum dot. A magnetic field is applied perpendicularly to the electron plane
of motion. We show that the energy levels corresponding to states with high
angular momentum, J, and a low number of vibrational quanta may be
systematically computed as power series in 1/|J|. These states are relevant in
the high-B limit.Comment: LaTeX, 15 pages,6 postscript figure
Magnetized strange quark matter and magnetized strange quark stars
Strange quark matter could be found in the core of neutron stars or forming
strange quark stars. As is well known, these astrophysical objects are endowed
with strong magnetic fields which affect the microscopic properties of matter
and modify the macroscopic properties of the system. In this paper we study the
role of a strong magnetic field in the thermodynamical properties of a
magnetized degenerate strange quark gas, taking into account beta-equilibrium
and charge neutrality. Quarks and electrons interact with the magnetic field
via their electric charges and anomalous magnetic moments. In contrast to the
magnetic field value of 10^19 G, obtained when anomalous magnetic moments are
not taken into account, we find the upper bound B < 8.6 x 10^17 G, for the
stability of the system. A phase transition could be hidden for fields greater
than this value.Comment: 9 pages, 9 figure
How many Ultra High Energy Cosmic Rays could we expect from Centaurus A?
The Pierre Auger Observatory has associated a few ultra high energy cosmic
rays with the direction of Centaurus A. This source has been deeply studied in
radio, infrared, X-ray and -rays (MeV-TeV) because it is the nearest
radio-loud active galactic nuclei.
Its spectral energy distribution or spectrum shows two main peaks, the low
energy peak, at an energy of eV, and the high energy peak, at about
150 keV.
There is also a faint very high energy (E 100 GeV) -ray
emission fully detected by the High Energy Stereoscopic System experiment. In
this work we describe the entire spectrum, the two main peaks with a
Synchrotron/Self-Synchrotron Compton model and, the Very High Energy emission
with a hadronic model. We consider p and interactions. For the
p interaction, we assume that the target photons are those produced at
150 keV in the leptonic processes. On the other hand, for the pp interaction we
consider as targets the thermal particle densities in the lobes. Requiring a
satisfactory description of the spectra at very high energies with p
interaction we obtain an excessive luminosity in ultra high energy cosmic rays
(even exceeding the Eddington luminosity). However, when considering pp
interaction to describe the -spectrum, the obtained number of ultra
high energy cosmic rays are in agreement with Pierre Auger observations.
Moreover, we calculate the possible neutrino signal from pp interactions on a
Km neutrino telescope using Monte Carlo simulations.Comment: Accepted in Ap
Constraints on the braneworld from compact stars
According to the braneworld idea, ordinary matter is confined on a
3-dimensional space (brane) that is embedded in a higher-dimensional space-time
where gravity propagates. In this work, after reviewing the limits coming from
general relativity, finiteness of pressure and causality on the brane, we
derive observational constraints on the braneworld parameters from the
existence of stable compact stars. The analysis is carried out by solving
numerically the brane-modified Tolman-Oppenheimer-Volkoff equations, using
different representative equations of state to describe matter in the star
interior. The cases of normal dense matter, pure quark matter and hybrid matter
are considered.Comment: 13 pages, 11 figures, 2 tables; new EoS considered, references and
comments adde
Calorons on the lattice - a new perspective
We discuss the manifestation of instanton and monopole solutions on a
periodic lattice at finite temperature and their relation to the infinite
volume analytic caloron solutions with asymptotic non-trivial Polyakov loops.
As a tool we use improved cooling and twisted boundary conditions. Typically we
find 2Q lumps for topological charge Q. These lumps are BPS monopoles.Comment: Latex. 16 pages, 9 figure
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